1. Field of the Invention
This invention pertains generally to supports for vehicle seats and, in particular, to a cushion and height adjustment device for seats generally used in vehicles such as buses, trucks, off-the-road construction type vehicles, and farm vehicles.
2. Description of the Prior Art
Some prior art seat cushioning devices use coil springs or pneumatic air bags to support a seat. The cushioning devices provide a fixed spring rate or cushioning effect aimed at producing a comfortable ride for an occupant of average size and height. Such cushioning devices are unacceptable because of the variations in sizes and weights of vehicle operators who normally occupy this type of seat. In the event an extremely heavy operator were to sit on a seat designed for an average weight person, he would feel uncomfortable at best, and, at worst, there could be no spring effect at all because the springs could bottom out during travel over extremely rough terrain. On the other hand, a very lightweight operator would receive an extremely stiff ride from seat cushion springs designed for the seat occupant of average weight.
Furthermore, seat cushioning devices having a variable or adjustable spring rate cannot be easily adjusted vertically, after spring adjustment, for each individual seat occupant without changing the cushioning of the seat.